1. Field of the Invention
The present invention relates to a machining method and machining system for micromachining a part in a machine component.
2. Description of the Related Art
In the past, known drilling and electrodischarge machining have been used for precision machining for forming micro through holes and micro grooves in various machine components.
Drilling requires a drill to be smaller in diameter the smaller the diameter of the hole that it is used for. This raises the drill breakage rate and increases the rate of occurrence of defects in machine components.
Further, electrodischarge machining requires, due to the properties of electromachining, a several dozen to several hundred μm gap (electrodischarge gap) between a machining point and electrode, so the smaller the hole diameter, the finer the electrode that is necessary. Such ultra micro electrodes are incapable of applying a high voltage. Further, the electrodes are not reusable and are extremely expensive, so the running costs rise.
Thus, the assignee focused on a water jet guided laser machining system as a method of machining as an alternative to electrodischarge machining, drilling, and the like (see Japanese Patent Publication (A) No. 2008-6471). That is, a water jet guided laser machining system is a system ejecting high-pressure water from a high-pressure water feed unit as a cylindrical-shaped water column to a machining point and firing a laser beam from a laser generating unit using the water column as a waveguide.
According to such a water jet guided laser machining system, the water column ejected at the machining point has a cylindrical shape. The laser beam progresses while being totally reflected inside the cylindrical water column, so the straightness is high. Accordingly, this enables accurate positioning of the machining point. Further, energy concentrates within the water column, so machining with good efficiency and high precision can be expected.
Water jet guided laser machining has advantages over electrodischarge machining in this respect, but the range of each machining operation is limited to the range of the cross-sectional area of the water column, so formation of any shapes or dimensions of holes or grooves for a machine component requires moving the water jet and laser generating unit or the machine component.
Further, at that time, it is necessary to be careful with the rate of attenuation of the laser power at the machining surface and deep parts. The water jet guided laser machining method uses a thin water jet as a waveguide for the laser beam. The water jet reaches a deep part while impacting walls of an ultrathin span, so the water jet is disturbed at the deep part region and therefore the efficiency drops. That is, it is believed that there is a tendency for the surface roughness to become rougher at the vicinity of a deep part than at the vicinity of the surface of a workpiece.